Abstract

Core-shell SiO2/Au nanocylinder arrays (NCAs) are studied using finite-difference time-domain simulations. The increase of height induces new surface plasmon resonances along the nanocylinders, i.e., dipole and quadrupole modes. Orthogonal coupling between superstrate diffraction order and the height-induced dipole mode is observed, which could achieve a well-defined lattice plasmon mode even for smaller NCAs in asymmetric environments. Electromagnetic field distribution has been employed to determine the coupling origin. Radiative loss could also be effectively suppressed in these core-shell NCAs, indicating the possibility of future applications in fluorescence enhancement and nanolasers.

Figures (5)

Schematic view of the core-shell SiO2/Au NCAs on the glass substrate. d∥ and d⊥ denote the distance between the neighboring NCs along or vertical to the direction of external electric field E. h indicates the height of the NCs. Inset shows the cross section of the core-shell structure, and D represents the diameter of the SiO2 NCs.

(a) Extinction cross section of the core-shell SiO2/Au NCAs with D=200nm, d∥=d⊥=500nm, and different heights. (b)–(d) correspond to the distribution of Ex component for the plasmon modes at 660, 743, and 1034 nm, respectively, consistent with the extinction peaks shown in (a). Charge density distribution of (e) Q mode at 660 nm and (f) D2 mode at 743 nm.